This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Many oil producing countries are experiencing strong domestic growth in power demand and have an interest in enhanced oil recovery (EOR) to improve oil recovery from their reservoirs. Two common EOR techniques include nitrogen (N2) injection for reservoir pressure maintenance and carbon dioxide (CO2) injection for miscible flooding for EOR. There is also a global concern regarding green house gas (GHG) emissions. This concern combined with the implementation of cap-and-trade policies in many countries makes reducing CO2 emissions a priority for these and other countries as well as the companies that operate hydrocarbon production systems therein.
Some approaches to lower CO2 emissions include fuel de-carbonization or post-combustion capture using solvents, such as amines. However, both of these solutions are expensive and reduce power generation efficiency, resulting in lower power production, increased fuel demand and increased cost of electricity to meet domestic power demand. In particular, the presence of oxygen, sulfur oxides (SOX), and nitrogen oxide (NOX) makes the use of amine solvent absorption very problematic. Another approach is an oxyfuel gas turbine in a combined cycle (e.g., where exhaust heat from the gas turbine Brayton cycle is captured to make steam and produce additional power in a Rankine cycle). However, there are no commercially available gas turbines that can operate in such a cycle and the power required to produce high purity oxygen significantly reduces the overall efficiency of the process.
Moreover, with the growing concern about global climate change and the impact of CO2 emissions, emphasis has been placed on minimizing CO2 emissions from power plants. Gas turbine power plants are efficient and have a lower cost compared to nuclear or coal power generation technologies. Capturing CO2 from the exhaust of a gas turbine power plant is very expensive, however, because the concentration of CO2 in the exhaust stack is low, a large volume of gas needs to be treated, and the pressure of the exhaust stream is low. These factors, among others, result in a high cost of CO2 capture.
Capture and recovery of CO2 from low emission power generation systems that incorporate an exhaust gas recycle loop has been previously described. For example, U.S. Patent Application Ser. No. 61/361,173, which is incorporated herein by reference in its entirety, illustrates the use of a potassium carbonate (K2CO3) solvent to absorb and recover CO2 from such systems. When CO2 is recovered via solvent absorption, however, the solvent also absorbs small quantities of volatile components (such as, for example, nitrogen, oxygen, argon, and carbon monoxide) that will have a small solubility in a water-based solvent such as K2CO3. Upon regeneration of the solvent to release the absorbed CO2, these volatile components will also be evolved and will remain with the CO2. If the CO2 is used for EOR or is injected into a reservoir for sequestration, the presence of volatiles may be undesirable. For example, the presence of oxygen may increase corrosion rates, while the presence of carbon monoxide (CO) may result in safety or environmental hazards if released during startup or process upset conditions.
Accordingly, there is still a substantial need for a low emission, high efficiency power generation process with incorporated CO2 capture and recovery at a reduced cost. Additionally, when a K2CO3 solvent is employed for CO2 separation, there is also an interest in removing volatiles from the recovered CO2.